package org.apache.helix.alerts;
   
   /*
    * Licensed to the Apache Software Foundation (ASF) under one
    * or more contributor license agreements.  See the NOTICE file
    * distributed with this work for additional information
    * regarding copyright ownership.  The ASF licenses this file
    * to you under the Apache License, Version 2.0 (the
    * "License"); you may not use this file except in compliance
   * with the License.  You may obtain a copy of the License at
   *
   *   http://www.apache.org/licenses/LICENSE-2.0
   *
   * Unless required by applicable law or agreed to in writing,
   * software distributed under the License is distributed on an
   * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
   * KIND, either express or implied.  See the License for the
   * specific language governing permissions and limitations
   * under the License.
   */
  
  import org.apache.helix.HelixException;
  
  
  public class AccumulateAggregator extends Aggregator {
  
  	
  	public AccumulateAggregator() 
  	{
  		_numArgs = 0;
  	}
  	
  	@Override
  	public void merge(Tuple<String> currValTup, Tuple<String> newValTup,
  			Tuple<String> currTimeTup, Tuple<String> newTimeTup, String... args) {
  	
  		double currVal = 0;
  		double currTime = -1;
  		double newVal;
  		double newTime;
  		double mergedVal;
  		double mergedTime;
  		
  		if (currValTup == null || newValTup == null || currTimeTup == null ||
  				newTimeTup == null) {
  			throw new HelixException("Tuples cannot be null");
  		}
  		
  		//old tuples may be empty, indicating no value/time exist
  		if (currValTup.size() > 0 && currTimeTup.size() > 0) {
  			currVal = Double.parseDouble(currValTup.iterator().next());
  			currTime = Double.parseDouble(currTimeTup.iterator().next());
  		}
  		newVal = Double.parseDouble(newValTup.iterator().next());
  		newTime = Double.parseDouble(newTimeTup.iterator().next());
  		
  		if (newTime > currTime) { //if old doesn't exist, we end up here
  			mergedVal = currVal+newVal; //if old doesn't exist, it has value "0"
  			mergedTime = newTime;
  		}
  		else {
  			mergedVal = currVal;
  			mergedTime = currTime;
  		}
  	
  		currValTup.clear();
  		currValTup.add(Double.toString(mergedVal));
  		currTimeTup.clear();
  		currTimeTup.add(Double.toString(mergedTime));
  	}
  
  	
  }